Sensor module and protective glass

ABSTRACT

A sensor module includes: a base member; at least one of a single or a plurality of sensors and vibrators arranged on the base member; and a protective member constituted of at least one flat surface or a curved surface, provided so as to cover the at least one of the sensors and the vibrators. A part or whole of the protective member is formed of a strengthened glass and the strengthened glass is a chemically strengthened glass or a physically strengthened glass.

TECHNICAL FIELD

The present invention relates to a sensor module accommodating thereinat least one of a sensor and a vibrator, and a protective glassprotecting a sensor or a vibrator.

BACKGROUND ART

A plurality of sensors having various functions are mounted on a car, anelectric train, a mobile equipment such as drone, and a security devicesuch as an outdoor sensor or a surveillance camera. A sensor moduleusing a resin cover as a protective member protecting those sensors isknown. When a sensor is arranged outdoors, it is required to select amaterial strong to weathering and heat shock, in addition to rigidityand scratch resistance of a protective member protecting a sensor.

The kind of the sensor arranged inside the protective member is animportant factor for selecting a structure and material of theprotective member. Uses of a sensor may be impaired depending on thestructure and material of the protective member. For example, as aprotective glass protecting the sensor, it is required to select amaterial having high transmitting property that transmits visible light.

A sensor using ultrasonic waves is known as a sensor that is mounted ona surveillance camera and a car (Patent Literature 1). The ultrasonicsensor described in Patent Literature 1 can receive ultrasonic wavesthat was sent from a transmitter element transmitting ultrasonic wavesand reflected by an object to be detected, by a receiving member havinga receiving part receiving ultrasonic wave.

Furthermore, ultrasonic waves are utilized in water repellency andcleaning of a window in addition to the measurement of a distance(Patent Literature 2). It can be expected that uses of the sensor usingultrasonic waves will be further expanded in future.

As a structure having a sensor arranged inside the protective member, astructure having a sensor arranged inside a protective member using aresin is known (Patent Literature 3). Patent Literature 3 discloses thatelectric continuity with electrodes of a vibrator arranged inside acasing is secured while using a resin casing as a protective memberaccommodating an ultrasonic sensor.

CITATION LIST Patent Literature

Patent Literature 1: JP-A-2007-174323

Patent Literature 2: JP-T-2016-531792 (the term “JP-T” as used hereinmeans a published Japanese translation of a PCT patent application)

Patent Literature 3: JP-A-2006-203563

SUMMARY OF INVENTION Technical Problem

However, the protective member using a resin described in PatentLiterature 3 had a problem that when the protective member was arrangedoutdoors, the protective member has low rigidity and does not haveexcellent scratch resistance and weather resistance.

The present invention has been completed in view of the above and has anobject to provide a sensor module having higher rigidity as comparedwith the case of using a resin as a protective member and havingexcellent scratch resistance and weather resistance, by using achemically strengthened glass as a protective member.

Solution to Problem

According to a certain aspect of the present invention, a sensor moduleincluding: a base member; at least one of a single or a plurality ofsensors and vibrators arranged on the base member; and a protectivemember constituted of at least one flat surface or a curved surface,provided so as to cover the at least one of the sensors and thevibrators, wherein a part or whole of the protective member is formed ofa strengthened glass and the strengthened glass is a chemicallystrengthened glass or a physically strengthened glass, is provided.

According to a certain aspect of the present invention, the sensormodule, wherein the strengthened glass has a surface compressive stressvalue of 400 MPa or more and a depth of compressive stress layer of 10μm or more, is provided.

According a certain aspect of the present invention, the sensor module,wherein the strengthened glass has the surface compressive stress valueof 600 MPa or more and the depth of compressive stress layer of 40 μm ormore, is provided.

According a certain aspect of the present invention, the sensor module,wherein the strengthened glass is a chemically strengthened glass andhas a thickness of from 0.5 mm to 3.5 mm, is provided.

According a certain aspect of the present invention, the sensor module,wherein the strengthened glass is a chemically strengthened glass, has athickness of from 1.5 mm to 3.5 mm, and has a depth of compressivestress layer in a range of from 200 μm to 580 μm, is provided.

According to a certain aspect of the present invention, the sensormodule, wherein the chemically strengthened glass has a surfacecompressive stress value of 700 MPa or more, is provided.

According a certain aspect of the present invention, the sensor module,wherein the chemically strengthened glass has the depth of thecompressive stress layer in a range of from 250 μm to 580 μm, and has acompressive stress value at a depth of 100 μm from a surface of 100 MPaor more, is provided.

According a certain aspect of the present invention, the sensor module,wherein the chemically strengthened glass has a curved surface shapehaving a convex surface and a concave surface, and a value obtained bysubtracting a surface compressive stress value of the concave surfacefrom a surface compressive stress value of the convex surface is 10 MPaor more, is provided.

According a certain aspect of the present invention, the sensor module,wherein a value obtained by subtracting a depth of compressive stresslayer of the concave surface from a depth of compressive stress layer ofthe convex surface is 10 μm or more, is 10 μm or more is provided.

According a certain aspect of the present invention, the sensor modulewherein the chemically strengthened glass has at least one bending pointin a region forming the compressive stress layer and has a stressdistribution curve having a different inclination with the bending pointas a boundary, is provided.

According a certain aspect of the present invention, the sensor module,wherein the vibrator has an ultrasonic generating element, is provided.

According a certain aspect of the present invention, the sensor module,wherein the protective member has a transparent heater, is provided.

According a certain aspect of the present invention, the sensor module,wherein the strengthened glass has a first main surface and a secondmain surface facing the first main surface, and has an end surfacebetween the first main surface and the second main surface, and the endsurface has a surface roughness in a range of from 0.01 μm to 1.0 μm, isprovided.

According a certain aspect of the present invention, the sensor module,wherein the strengthened glass is glass a ceramics, is provided.

According a certain aspect of the present invention, the sensor module,wherein the strengthened glass has a water-repellent film on the surfaceof the strengthened glass, is provided.

According a certain aspect of the present invention, a protective glassconstituted of a flat surface or a curved surface, wherein a part orwhole of the protective glass is a strengthened glass, and thestrengthened glass is a chemically strengthened glass or a physicallystrengthened glass, is provided.

According a certain aspect of the present invention, the protectiveglass having an ultrasonic vibrator is provided.

According a certain aspect of the present invention, the protectiveglass having a transparent heater is provided.

Advantageous Effects of Invention

The sensor module of the present invention uses a strengthened glass asa protective member and therefore has high surface strength and edgestrength, has high rigidity and scratch resistance and further has highweather resistance (weathering resistance and heat shock resistance).Therefore, the sensor module is suitable for arranging outdoors.

BRIEF DESCRIPTION OF DRAWINGS

(a) to (c) of FIG. 1 are perspective views showing one example of theconfiguration of a sensor module in the embodiment of the presentinvention.

FIG. 2 is a side view showing one example of the configuration of amounting part in this embodiment.

(a) and (b) of FIG. 3 are perspective views showing one example of apower supply mechanism of the mounting part in this embodiment. (a) ofFIG. 3 shows a wired power supply and (b) of FIG. 3 shows a wirelesspower supply.

(a) and (b) of FIG. 4 are perspective views showing one example of thearrangement of a vibrator or a transparent heater in this embodiment.

DESCRIPTION OF EMBODIMENTS

Preferred embodiment of the present invention is described by referenceto the drawings. In the description of reference signs in the drawings,the same or corresponding reference signs are allotted to the same orcorresponding members or parts, and duplicate descriptions are omitted.

Furthermore, the expression “from . . . to” showing a numerical range inthe present description is used in the meaning of including thenumerical values indicated before and after “to” as the lower limit andthe upper limit.

<Sensor Module>

The sensor module of this embodiment includes a base member 15, at leastone of a single or a plurality of sensors 20 and vibrators 40 arrangedon the base member 15, and a protective member 1 constituted of at leastone of a flat surface and a curved surface, provided so as to cover theat least one of the sensor 20 and the vibrator 40. The elementsconstituting the sensor module of this embodiment are described indetail below.

<Protective Member 1>

(a) and (b) of FIG. 1 are perspective views showing one example of theconfiguration of a protective member 1 in this embodiment. (a) of FIG. 1is a structure using a protective glass 10 as a lid part of acylindrical casing (protective member 1) accommodating a sensor 20. (b)of FIG. 1 is a structure using a glass as a spherical surface of ahemisphere accommodating the sensor 20. A part or the whole of theprotective member 1 is formed using the protective glass 10, but asupport part 2 supporting the protective glass 10 may be formed in apart of the protective member 1 as shown in (a) of FIG. 1. The supportpart 2 may be a glass, but a metal such as stainless steel or alumitemay be used. The protective member 1 is not limited to a cylindricalshape or a hemisphere, and may be a columnar shape, a prismatic shapeand a three-dimensional shape such as a spherical regular polyhedron((c) of FIG. 1). The protective member 1 can be formed by laminating aplurality of glasses. In the case of forming the support part 2, anadhesive layer is formed between the support part 2 and the protectiveglass 10, thereby sticking the support part 2 to the protective glass10.

The protective member 1 accommodates the sensor 20 having detectingfunction or sensing function using millimeter wave, ultrasonic wave,visible light, infrared light or LIDAR or comprehensively using those.In the case where the sensor module of this embodiment is arrangedoutdoors, the protective member 1 as a casing is required to protect themounting part 5 from climatic factors such as rain and snow and externalfactors such as shock by stepping stone. Therefore the protective member1 requires certain strength against those factors.

The adhesive layer (not shown) sticking the protective glass 10 to thesupport part 2 preferably contains at least one selected from the groupconsisting of a polyvinyl acetate resin, a polyvinyl chloride resin, apolyvinyl alcohol resin, an ethylene copolymer resin, a polyacrylic acidester resin, a cyanoacrylate resin, a saturated polyester resin, apolyamide resin, a linear polyimide resin, a melamine resin, a urearesin, a phenol resin, an epoxy resin, a polyurethane resin, anunsaturated polyester resin, a reactive acrylic resin, a rubber resin, asilicone resin, a modified silicone resin, a glass frit and a solder. Byforming an adhesive layer made of a material that does not deform anddoes not weather even though arranged outdoors, using the resins and thelike described above, durability of the protective member 1 can beenhanced.

When the protective member 1 has a transparent heater 60, the protectivemember can exhibit functions of anti-fogging and snow melting and canprevent that the sensor does not work by fogging and snow. Thus, this ispreferred (see (a) of FIG. 4 and (b) of FIG. 4). The transparent heateris, for example, a transparent electrode of ITO or the like deposited ata sensor side of the protective member 1, and an electric current isapplied to the transparent electrode, thereby generating heat. Waterdroplets and snow are evaporated by the heat, and water droplets andsnow can be removed from the surface of the protective member 1. Inorder to exhibit the similar functions, a non-transparent metal may beused as a heater. In this case, the portion other than a window used forthe sensor may be covered with the non-transparent metal, and the metalmay be functioned as a heater.

<Protective Glass 10>

The protective glass 10 can be formed by subjecting a glass obtainedthrough each step of cutting a large-sized plate glass into small size,followed by machining and polishing, and subjecting strengtheningtreatment such as chemical strengthening or physical strengthening. Asthe cutting method of the plate glass, for example, cutting by diamondblade, or a scribe cleaving method, a laser cutting method and the likecan be applied. In case where strength of the protective glass 10desired to be increased, a surface layer part of the protective glass 10is preferably chemically strengthened or physically strengthened, andmore preferably all of the surface layer part is chemically strengthenedor physically strengthened. As a tool for applying machining orpolishing to the protective glass, whetstone can be used. Other thanthis, a buff, a brush and the like formed of cloth, leather, rubber orthe like can be used. In this case, an abrasive such as cerium oxide,alumina, carborundum or colloidal silica can be used. Above all,whetstone is preferably used as a polishing tool from the standpoint ofdimensional stability.

In the protective glass 10, adhesiveness between the support part 2 andthe mounting part 5 is improved by roughening the portion contacting thesupport part 2 or the mounting part 5 (for example, the portioncorresponding to the end surface of the protective glass). The shape ofthe protective glass 10 is not particularly limited so long as theprotective glass has a first main surface, a second main surface facingthe first main surface and an end surface between the first main surfaceand the second main surface. For example, in the case where theprotective glass 10 as a hemisphere shown in (b) of FIG. 1 is viewedfrom the side of a concave surface, when the portion (end surface)drawing a circle with a predetermined width is roughened, adhesivenessbetween the surface showing the circle and the facing portion to bebonded is improved, thereby facilitating the fixation. As a result, theprotective glass 10 can be stably mounted. The level of roughening isspecifically that a surface roughness Ra is 0.01 μm or more, preferably0.05 μm or more, more preferably 0.1 μm or more and still morepreferably 0.2 or more. When the end surface is excessively roughened,the adhesiveness between the end surface and the facing portion may beimpaired. Therefore, surface roughness Ra of the end surface is 1.0 μmor less, preferably 0.5 μm or less and more preferably 0.4 μm or less.In the case where the support part 2 is constituted of a strengthenedglass, the surface roughness Ra of the end surface of the support part 2is preferably within the above range. The surface roughness Ra in thepresent description means arithmetic mean roughness defined in JISB0601:2001.

The protective glass is not limited to the hemispherical protectiveglass 10 represented by (b) of FIG. 1. Other than a hemisphere, when adome-shaped protective glass having a curved surface shape is used, inthe case where the sensor 20 is a camera for visible light, theprotective glass has the effect of expanding an imaging range (a fieldof view), which is preferred. In the case where the protective glass hasa dome shape (curved surface shape), its size is not particularlylimited. For example, an outer diameter is a range of from 10 to 30 mmand an inner diameter is a range of from 5 to 30 mm. When a dome-shapedglass plate including a hemisphere is processed to a dome shape and thensubjected to a chemical strengthening treatment, large surfacecompressive stress is obtained at the side of a convex surface of thechemically strengthened glass plate as compared with the side of aconcave surface thereof by shape effect. Furthermore, in the chemicallystrengthened glass plate, large depth of a compressive stress layer isobtained at the side of a convex surface as compared with the side of aconcave surface thereof. For this reason, when the protective glass isparticularly placed in outdoor environment, larger strengthening isobtained at the side of a convex surface corresponding to the side of afront surface, and this is preferred. The dome-shaped glass plate canrealize desired surface compressive stress and depth of a compressivestress layer by appropriately adjusting the conditions of the chemicalstrengthening treatment.

In particular, in the case of chemically strengthening a dome-shapedglass plate, a value obtained by subtracting a surface compressivestress value of a concave surface from a surface compressive stressvalue of a convex surface is preferably 10 MPa or more, more preferably15 MPa or more and still more preferably 20 MPa or more. Furthermore, avalue obtained by subtracting DOL of a concave surface from DOL of aconvex surface is preferably 10 μm or more, more preferably 20 μm ormore and still more preferably 40 μm or more.

The dome-shaped protective glass 10 can be obtained by, for example,bending. Preferred embodiment of the bending is described below, but amethod for obtaining a curved surface shape protective glass 10 in thisembodiment is not limited to the embodiment described below.

In the bending, a glass is placed on a mold constituted of carbon,heated to a temperature region of from 600 to 950° C., hot-pressed forfrom 30 to 180 seconds while maintaining the temperature, and thengradually cooled. Thus, a curved surface shape glass plate is formed.The curved surface shape glass plate is cut into a desired externalform, and the surface of the glass plate is polished. Thus, the curvedsurface shape protective glass 10 such as a dome-shaped protective glass10 having a desired shape and a desired surface roughness is obtained.

The method for obtaining the curved surface shape protective glass 10 isnot limited to bending, and is obtained by, for example, cutting of athick glass plate.

The protective glass 10 may further have a water-repellent film (notshown) on the main surface thereof. Material of the water-repellent filmis specifically a material having high water repellency, and ispreferably a material further having an antifouling property. Examplesof such materials of the water-repellent film include afluorine-containing organic material and a fluorine resin, and morepreferably include a fluorine-containing organic silicon compound and afluorine-containing organic compound having hydrolyzability. Thicknessof the water-repellent film is not particularly limited so long astransmitting property of the protective glass 10 is not impaired. Forexample, when the thickness is 10 nm or more, the effect of waterrepellency can be exhibited, and this is preferred. The thickness ismore preferably 100 nm or more. The upper limit of the thickness of thewater-repellent film is not particularly limited, but is preferably 1 μmor less from the standpoint of productivity.

The protective glass 10 is preferably constituted of a glass having hightransparency. A multicomponent oxide glass can be used as a material ofa glass used as the protective glass 10.

Specific examples of the composition of the glass used as the protectiveglass 10 are shown below, but the composition of the glass is notlimited to those. The glass used in the present invention is notparticularly limited so long as it contains sodium, and glasses havingvarious compositions can be used so long as the glasses contain acomposition that can be molded and strengthened by a chemicalstrengthening treatment or a physical strengthening treatment.

Specifically, examples of the glass include aluminosilicate glass, sodalime glass, borosilicate glass, lead glass, alkali barium glass,aluminoborosilicate glass, glass ceramics and alkali-containing opticalglass. Of those, glass ceramics has relatively high strength. Therefore,when the glass ceramics is subjected to a physical strengtheningtreatment or a chemical strengthening treatment, a strengthened glasshaving higher strength is easily obtained.

Glass ceramics is that crystals are precipitated in a glass. As comparedwith an amorphous glass free of crystal, the glass ceramics is hard anddifficult to be scratched. Furthermore, when the glass ceramics aresubjected to an ion-exchange treatment to be chemically strengthened,strength can be further enhanced.

The glass ceramics can be obtained by heat-treating an amorphous glassunder appropriate conditions. For example, glass ceramics having visiblelight haze value of 1.0% or less in terms of 0.8 mm thickness is usefulas the protective glass 10. The haze value can be measured, for example,using illuminant C that is the standard of standard illuminant definedin CIE, using a haze meter “HZ-2” manufactured by Suga Test InstrumentsCo., Ltd.

One example of the composition of the glass used as the protective glass10 contains, in mass percentage on oxide basis, SiO₂: from 56 to 66%,Al₂O₃: from 8 to 18%, Na₂O: from 9 to 17%, K₂O: from 1 to 11%, MgO: from2 to 12%, CaO: from 0 to 5%, SrO: from 0 to 5%, BaO: from 0 to 5% andZrO₂: from 0 to 5%.

One example of the composition of the glass used as the protective glass10 contains, in mass percentage on oxide basis, SiO₂: from 58 to 65%,Al₂O₃: from 14 to 21%, Na₂O: from 12 to 19%, MgO: from 3 to 10%, K₂O:from 0.5 to 1.3%, ZrO₂: from 0.1 to 0.5% and TiO₂: from 0.0 to 0.1%.

One example of the composition of the glass used as the protective glass10 contains, in mass percentage on oxide basis, SiO₂: from 55 to 65%,Al₂O₃: from 12 to 22%, Na₂O: from 10 to 20%, K₂O: from 0 to 2%, MgO:from 1 to 9% and ZrO₂: from 0 to 5%.

One example of the composition of the glass used as the protective glass10 contains, in mass percentage on oxide basis, SiO₂: from 55 to 65%,Al₂O₃: from 12 to 22%, Na₂O: from 10 to 20%, K₂O: from 0 to 2%, MgO:from 1 to 9%, ZrO₂: from 0 to 1% and TiO₂: from 0 to 1%.

One example of the composition of the glass used as the protective glass10 contains, in mass percentage on oxide basis, SiO₂: from 60 to 70%,Al₂O₃: from 9 to 19%, Na₂O: from 9 to 19%, K₂O: from 0 to 4%, MgO: from3 to 6%, CaO: from 0 to 1% and ZrO₂: from 0 to 1%.

One example of the composition of the glass used as the protective glass10 contains, in mass percentage on oxide basis, SiO₂: from 45 to 70%,B₂O₃: from 1 to 9%, Al₂O₃: from 15 to 25%, Na₂O: from 7 to 18%, K₂O:from 0 to 1%, MgO: from 0 to 5%, CaO: from 0 to 1% and TiO₂: from 0 to1%.

One example of the composition of the glass used as the protective glass10 contains, in mass percentage on oxide basis, SiO₂: from 45 to 70%,B₂O₃: from 1 to 9%, Al₂O₃: from 15 to 25%, Na₂O: from 7 to 18%, K₂O:from 0 to 1%, MgO: from 0 to 5%, CaO: from 0 to 1% and SnO₂: from 0 to1%.

One example of the composition of the glass used as the protective glass10 contains, in mass percentage on oxide basis, SiO₂: from 50 to 80%,Al₂O₃: from 1 to 30%, B₂O₃: from 0 to 6%, P₂O₅: from 0 to 6%, Li₂O: from0 to 20%, Na₂O: from 0 to 20%, K₂O: from 0 to 10%, MgO: from 0 to 20%,CaO: from 0 to 20%, SrO: from 0 to 20%, BaO: from 0 to 15%, ZnO: from 0to 10%, TiO₂: from 0 to 5% and ZrO₂: from 0 to 8%.

One example of the composition of the glass used as the protective glass10 contains, in mass percentage on oxide basis, SiO₂: from 65 to 75%,Al₂O₃: from 1 to 5%, Na₂O: from 7 to 17%, K₂O: from 0 to 1%, MgO: from 3to 6% and CaO: from 6 to 9%.

One example of the composition of the glass used as the protective glass10 contains, in mass percentage on oxide basis, SiO₂: from 65 to 75%,Al₂O₃: from 3 to 10%, Na₂O: from 7 to 17%, K₂O: from 0 to 1%, MgO: from3 to 6%, CaO: from 6 to 9% and ZrO₂ as a trace component: from 0 to 1%.

Composition range of each component in the glass composition of theprotective glass 10 of this embodiment having the above-describedcomponents and other optional components are described below. The unitof content in each composition is mass percentage or mass ppm, on oxidebasis and is simply represented by “%” and “ppm”, respectively.

SiO₂ is a main component of the glass. The SiO₂ content is preferably45% or more, more preferably 55% and still more preferably 60% or morein order to maintain weather resistance of the glass and preventdevitrification.

On the other hand, the SiO₂ content is preferably 80% or less and morepreferably 70% or less in order to facilitate melting and enhance foamquality.

Al₂O₃ is an essential component for improving weather resistance of theglass. In the glass of this embodiment, the Al₂O₃ content is preferably7% or more and more preferably 10% or more in order to maintainpractically necessary weather resistance.

The Al₂O₃ content is preferably 30% or less, more preferably 23% or lessand still more preferably 20% or less in order to enhance opticalproperties and enhance foam quality.

B₂O₃ is a component accelerating melting of glass raw materials andenhancing mechanical properties and weather resistance. The B₂O₃ contentis preferably 6% or less and more preferably 3% or less in order toprevent the occurrence of disadvantages such as formation of striae(ream) by volatilization and corrosion of a furnace wall.

Alkali metal oxides such as Li₂O, Na₂O and K₂O are componentsaccelerating melting of glass raw materials and adjusting thermalexpansion, viscosity and the like.

The Na₂O content is preferably 8% or more and more preferably 10% ormore.

The K₂O content is preferably 3% or less and more preferably 1% or less.

Li₂O is an optional component but facilitates vitrification and reducesan iron content contained as impurities derived from raw materials.Therefore, the protective glass 10 of this embodiment can contain Li₂Oin an amount of 2% or less.

The total content of those alkali metal oxides (Li₂O+Na₂O+K₂O) ispreferably from 5 to 20% and more preferably from 8 to 15% in order toretain clarity when melting and maintain foam quality of the glassproduced.

Alkaline earth metal oxides such as MgO, CaO, SrO and BaO are componentseffective to accelerate melting of glass raw materials and adjustthermal expansion, viscosity and the like.

MgO has a function of decreasing a viscosity when melting a glass andaccelerating melting. MgO further has a function of decreasing aspecific gravity and making it difficult to cause flaws on theprotective glass 10. The MgO content is preferably 10% or less and morepreferably 8% or less in order to decrease a coefficient of thermalexpansion of the glass and prevent devitrification.

CaO is a component accelerating melting of glass raw materials andadjusting a viscosity, thermal expansion and the like. To achieve theabove functions, the CaO content is preferably 0.5% or more and morepreferably 1% or more. On the other hand, the CaO content is preferably6% or less and more preferably 4% or less in order to preventdevitrification and obtain satisfactory transmitting property.

SrO has an effect increasing a coefficient of thermal expansion anddecreasing high temperature viscosity of a glass. To achieve the effect,the protective glass 10 of this embodiment can contain SrO. The SrOcontent is preferably 3% or less and more preferably 1% or less in orderto reduce a thermal expansion coefficient of a glass.

Similar to SrO, BaO has an effect increasing a thermal expansioncoefficient and decreasing high temperature viscosity of a glass. Toachieve the effect, the protective glass 10 of this embodiment cancontain BaO. However, the BaO content is preferably 5% or less and morepreferably 3% or less in order to suppress a thermal expansioncoefficient of a glass low.

The total content of those alkaline earth metal oxides (MgO+CaO+SrO+BaO)is preferably from 1 to 15% and more preferably from 3 to 10% in orderto reduce a coefficient of thermal expansion, prevent devitrificationand maintain strength.

In the composition of the protective glass 10 of this embodiment, ZrO₂may be contained as an optional component in an amount of preferably 10%or less and more preferably 5% or less in order to enhance heatresistance and surface hardness of a glass. When the ZrO₂ content is 10%or less, the glass is difficult to devitrify.

The protective glass 10 of this embodiment may contain SO₃ as a refiningagent. In this case, the SO₃ content is, in mass percentage, preferablymore than 0% and less than 0.5%. The SO₃ content is more preferably 0.4%or less, still more preferably 0.3% or less and still further preferably0.25% or less.

The protective glass 10 of this embodiment may contain at least one ofSb₂O₃, SnO₂ and As₂O₃ as an oxidizing agent and a fining agent. In thiscase, each content of Sb₂O₃, SnO₂ and As₂O₃ is, in mass percentage,preferably from 0 to 0.5%. Each content is more preferably 0.2% or lessand still more preferably 0.1% or less. Sill further preferably, thoseare not substantially contained.

The protective glass 10 of this embodiment may contain NiO. When NiO iscontained, NiO further functions as a coloring component. Therefore, theNiO content is preferably 10 ppm or less based on the total amount ofthe glass composition.

The protective glass 10 of this embodiment may contain Cr₂O₃. When Cr₂O₃is contained, Cr₂O₃ further functions as a coloring component.Therefore, the Cr₂O₃ content is preferably 10 ppm or less based on thetotal amount of the glass composition.

The protective glass 10 of this embodiment may contain MnO₂. When MnO₂is contained, MnO₂ further functions as a visible light-absorbingcomponent. Therefore, the MnO₂ content is preferably 50 ppm or lessbased on the total amount of the glass composition.

The protective glass 10 of this embodiment may contain TiO₂. When TiO₂is contained, TiO₂ further functions as a visible light-absorbingcomponent. Therefore, the TiO₂ content is preferably 1000 ppm or lessbased on the total amount of the glass composition.

The protective glass 10 of this embodiment may contain at least onecomponent selected from the group consisting of CoO, V₂O₅ and CuO. Whenthose components are contained, those components further function as avisible light-absorbing component, thereby decreasing visible lighttransmittance. Therefore, the content of those components is preferably10 ppm or less based on the total amount of the glass composition.

<Chemical Strengthening Treatment>

The chemical strengthening treatment is conducted by immersing a glasscontaining sodium in a molten salt containing specific salt or base andhaving a temperature equal to or lower than a glass transitiontemperature, thereby ion-exchanging sodium ions with potassium ionshaving larger atomic radius. When a glass containing lithium ischemically strengthened, the chemical strengthening treatment conductedby ion-exchanging lithium ions with sodium ions having larger atomicradius. In the case of the glass containing both sodium and lithium, thechemical strengthening treatment may include two treatments of atreatment of ion-exchanging sodium ions with potassium ions andion-exchanging lithium ions with sodium ions.

The chemical strengthening step is, for example, a step of bringing aglass containing sodium into contact with an inorganic salt containingat least one salt or base selected from the group consisting ofpotassium nitrate, sodium nitrate, K₂CO₃, Na₂CO₃, KHCO₃, NaHCO₃, K₃PO₄,Na₃PO₄, K₂SO₄, Na₂SO₄, KOH and NaOH to conduct ion-exchange between Naions in the glass and K ions in the inorganic salt, thereby forming acompressive stress layer in the glass surface.

In the chemically strengthened glass obtained by the chemicalstrengthening treatment, a stress profile formed (a vertical axis is acompressive stress value (CS) and a horizontal axis is a depth of acompressive stress layer (DOL)) changes by controlling time andtemperature of the ion exchange, a salt used and other treatmentconditions. For example, in the case where a stress value of thechemically strengthened glass, obtained by conducting an ion exchangetreatment of ion-exchanging lithium ions with sodium ions and an ionexchange treatment of ion-exchanging sodium ions with potassium ions toone glass, is measured, the stress profile draws a bent profile havingdifferent inclination with the bending point as a boundary. In otherwords, when the combination of ion-exchange to the glass is two or moregroups and two or more kinds of ions in the glass are ion-exchanged, adepth of the compressive stress layer can be increased while increasingthe surface compressive stress value, and a high strength chemicallystrengthened glass is obtained. Examples of the ion-exchange methodinclude a method of immersing a glass in a molten salt containing twokinds of ions and a method of immersing a glass in multistage usingdifferent two or more kinds of molten salts. Thus, a stress profile inwhich the bending point is present as described above is obtained bypassing through a process giving two or more groups of the combinationof ion-exchanges.

When the surface of a glass is ion-exchanged and a surface layer havingcompressive stress remained therein is formed, compressive stressremains in the surface of a glass and strength of the glass is enhanced.The strengthened glass obtained changes depending on a thickness of aglass and its composition, and is appropriately designed so as to besurely strengthened depending on uses of the glass.

The chemical strengthening treatment is preferably conducted at atemperature in a range of from 300 to 500° C. from the standpoint ofpreventing change in quality (weathering) due to elution of an alkali inthe chemically strengthened glass obtained by the chemical strengtheningtreatment. A salt such as hydrogen sulfate having the effect ofpreventing elution of an alkali may be added to a molten salt.

The thickness t of the chemically strengthened glass according to thisembodiment contributes to reduction in weight, and therefore isgenerally 3.5 mm or less and preferably 2.5 mm or less. The thickness tis more preferably 2.0 mm or less, still more preferably 1.7 mm or less,still further preferably 1.5 mm or less, still further preferably 1.3 mmor less and particularly preferably 1.0 mm or less. The glass having thethickness t of less than 0.5 mm is easy to be broken. Therefore, thethickness t is preferably 0.5 mm or more.

The chemically strengthened glass according to this embodiment has acompressive stress layer in the surface thereof by the ion-exchangetreatment. When a surface compressive stress value is high, the glass isdifficult to be broken by curved mode. For this reason, the surfacecompressive stress value of the chemically strengthened glass ispreferably 200 MPa or more, and more preferably 400 MPa or more, 600 MPaor more, 800 MPa or more, 900 MPa or more, 1000 MPa or more and 1100 MPaor more, in this order.

In the case where flaws having a depth exceeding the value of a depth ofthe compressive stress layer (DOL) are formed during the use of thechemically strengthened glass, breakage of the chemically strengthenedglass is easy to occur. For this reason, the DOL of the chemicallystrengthened glass is preferably large. The DOL is preferably 10 μm ormore, and more preferably 40 μm or more, 60 μm or more, 70 μm or more,80 μm or more, 90 μm or more, 100 μm or more, 110 μm or more, 120 μm ormore, 130 μm or more, 140 μm or more, 150 μm or more, 200 μm or more,300 μm or more, 400 μm or more, 500 μm or more and 550 μm or more, inthis order.

In particular, in the chemically strengthened glass used in theprotective glass of this embodiment, when the combination of thethickness t and the DOL is a combination of thickness t being in a rangeof from 1.5 to 3.5 mm and the DOL being in a range of from 200 to 580μm, the chemically strengthened glass is difficult to be broken even inoutdoor environment, and this is preferred. The combination of thethickness t and the DOL is preferably a combination of the thickness tbeing in a range of from 1.8 to 3.5 mm and the DOL being in a range 250to 580 μm and more preferably a combination of the thickness t being ina range of from 2.0 to 3.5 mm and the DOL being in a range of from 300to 580 μm.

In the chemically strengthened glass used for the protective glass ofthis embodiment, in addition to the relationship between the thickness tand the DOL, the surface compressive stress value is preferably 700 MPaor more, more preferably 800 MPa or more and still more preferably 900MPa or more.

In the chemically strengthened glass used for the protective glass ofthis embodiment, in addition to the relationship among the thickness t,the DOL and the surface compressive stress value, the compressive stressvalue at a depth of 100 μm from the surface is preferably 100 MPa ormore and more preferably 105 MPa or more.

In the case where the strengthened glass is a physically strengthenedglass, similar to the above, the surface compressive stress value andthe depth of compressive stress are preferably the above ranges. In thecase where the glass is physically strengthened, the temperatureconditions are set such that the glass surface is cooled rapidly and thetemperature inside the glass is gradually decreased, thereby obtaining a(physically) strengthened glass. In this case, the glass surface returnsto room temperature in an elongated state and the inside of the glassgradually shrinks. As a result, a compressive stress layer is generatedin the surface and tensile stress is generated in the inside of theglass. The characteristics of the physically strengthened glass are thatthe surface compressive stress is small but compressive stress is deeplypresent. For example, the surface compressive stress value is about 200MPa and the depth of the compressive stress layer is 100 μm or more.Furthermore, for example, the surface compressive stress value may befrom about 100 to 150 MPa and the depth of the compressive stress layermay be from ⅕ to ⅙ of the thickness of the glass.

The chemically strengthened glass preferably has at least one bendingpoint in a region forming the compressive stress layer when a stressprofile of vertical axis: CS and horizontal axis: DOL is given. When thechemically strengthened glass has a stress distribution curve havingdifferent inclination with the bending point as a boundary, thecompressive stress layer enters deeply and the glass is difficult to bebroken, which is preferred. As a result, the chemically strengthenedglass exhibits the effect of preventing cracking of the protective glassby stepping stone and the like.

As for the strength of the chemically strengthened glass and physicallystrengthened glass obtained, evaluation index by stepping stonedescribed before can be applied. Specifically, the strength can beevaluated based on SAE J400, JASO M104 and ISO 20567-1. For example,strength can be evaluated by confirming a cracked state when granite(gravel) having a size of from 9 to 15 mm as an emanation is ejected toa strengthened glass (including a dome shape) under 0.1 MPa, 0.2 MPa or0.4 MPa based on the conditions of JASO M104.

Surface roughness (Ra) of the protective glass 10 can be appropriatelyset. For example, the surface roughness of the protective glass 10 ispreferably 100 nm or less, more preferably 70 nm or less and still morepreferably 50 nm or less.

The protective glass 10 may have a structure in which a vibrator 40 isarranged such that the protective glass itself vibrates (see (a) of FIG.4 and (b) of FIG. 4). When the protective glass 10 is provided with thevibrator 40, the protective member 1 may be provided with or may not beprovided with the sensor 20. The vibrator 40 may be directly mounted onthe protective glass 10 or may be mounted on the support part 2. Theprotective glass 10 may have a vibration suppression function detectingvibration frequency and suppressing vibration. By this function,vibration damping of the protective glass 10 is prevented and givenvibration frequency can be maintained. The vibrator 40 may be apiezoelectric element or may be an element oscillating with stablevibration frequency, such as an electromagnetic actuator, a piezoelement, a crystal vibrator, a ceramic oscillator or a magnetostrictor.Thus, when the vibrator 40 vibrates, the protective glass functions as aspeaker, and when mounted on a car, vibration during running can besuppressed. Furthermore, as described later, strains attached to theprotective glass 10 can be removed.

<Sensor 20>

The sensor 20 accommodated has detecting function or sensing functionusing millimeter waves, ultrasonic waves, laser, visible light, infraredlight or LIDAR or comprehensively using those and can be used as anon-contact sensor of a light detection method, an ultrasonic method, amicrowave method, a laser method, a radiation method or an imagediscrimination method. For example, when the sensor 20 is mounted on acar, a distance to an adjacent vehicle approaching the car and anobstacle present in running direction can be measured using thedetecting function. Furthermore, an external arrangement mechanism maybe driven through a communication equipment arranged outside based on asignal transmitted by the sensor 20. For example, when the communicationequipment is a transducer arranged on a windshield, a wiper can bedriven and a heater can be operated, through the transducer.

The sensor 20 may be an ultrasonic sensor. Ultrasonic waves are utilizedfor the measurement of a distance and for water repellency and cleaningof a window, and always stable visibility and instrument display areobtained. In particular, when the sensor 20 is mounted on a car, thesensor can be applied to antifogging and snow melt by utilizing itscharacteristics.

When the sensor 20 is an ultrasonic sensor, it is known that ultrasonicwaves are attenuated as frequency band of ultrasonic waves transmittedand received is high. For this reason, ultrasonic waves of frequencyband lower than 100 KHz, such as from 1 KHz to 20 KHz or from 40 KHz to60 KHz, are actually utilized.

<Camera 30>

One or a plurality of camera 30 is present depending on its uses. Forexample, when the camera 30 is mounted on means of transportation, suchas a car or an electric train, or a mobile equipment such as a drone, aplurality of cameras may be arranged by use, such as for close rangemonitoring, forward monitoring and rear monitoring. Furthermore, animage and a video of approaching person and obstacle can be obtained byusing the camera in combination with the detection function or thesensing function by the sensor 20.

<Mounting Part 5>

FIG. 2 is a side view showing one example of sensor configuration inthis embodiment. The mounting part 5 is constituted of the sensor, thecamera 30 and a connecting part connecting those. Power supply of themounting part 5 may be wired power supply (see (a) of FIG. 3) and may bewireless power supply by external communication means using a sensorterminal (see (b) of FIG. 3). A plurality of sensors can be mounted byelectrical conduction by the powder supply mechanism of the mountingpart 5. In the connecting part connecting the sensor or camera 30, alead wire and may be used in the base member 15, a conductive materialmay be used for forming the connecting part.

The mounting part is arranged on the base member 15. Material of thebase member 15 may be silicon or glass, and other than those, may be ametal such as iron or aluminum. Alternatively, a conductive material maybe laid between the base member 15 and the mounting part. For example,when an ultrasonic sensor is mounted, a vibrator has, for example, anultrasonic generating element 50 and is fitted in the mounting part 5such that the ultrasonic generating element 50 does not expose outside.In this case, a material such as aluminum, glass, polyimide, silicon orpolycarbonate can be used for the vibrator.

<Driving Principle>

The ultrasonic generating element 50 as shown in FIG. 2 generallyutilizes a principle of applying high frequency voltage to apiezoelectric element to vibrate the piezoelectric element. Ultrasonicwaves generated by applying high frequency voltage to a piezoelectricelement to vibrate the piezoelectric element is transmitted to a targetobject to be measured and received as reflected waves reflected by theobject to be measured. As a result, for example, a distance to anapproaching adjacent vehicle or an obstacle present in a runningdirection can be measured. The ultrasonic generating element 50 isprovided with a transmitting part intermittently transmitting pulsesignals and a receiving part receiving its reflected waves and thereforefunctions as a sensor.

The ultrasonic generating element 50 may utilizes a principle that aheating element is driven by applying an electric current that changesin an ultrasonic cycle to the heating element from a power supply and asa result, a calorific value by the heating element follows the frequencyof an electric current and periodically changes. The periodical heatgenerated by the heating element is transmitted to the vibrator and thetemperature of the vibrator periodically changes. The vibrator repeatsthermal expansion and contraction periodically in a thickness directiondepending on its temperature and vibrates. Ultrasonic waves aregenerated from a vibrating surface of the vibrator by the vibration. Forthe heating element, an electrical resistor generating Joule heat, suchas aluminum may be used and Peltier element may be used.

The ultrasonic generating element 50 can detect reflected waves (from anobstacle or the like) using the receiving part equipped with apiezoelectric vibration detecting element. For example, thepiezoelectric vibration detecting element can be prepared on SOIsubstrate by MEMS technology and is formed by laminating so as tosandwich a piezoelectric thin film between a top electrode and a bottomelectrode. The piezoelectric thin film is, for example, lead zirconatetitanate (PZT), and the piezoelectric vibration detecting elementconverts a displacement of the vibrating part adjacently arranged intoan electrical signal and detects ultrasonic waves.

The piezoelectric vibration detecting element performs arithmeticprocessing based on an electric signal output into a circuit element toconduct amplification of a signal and removal of noises, and comparesphase difference and time difference between ultrasonic wavestransmitted from the transmitting part and ultrasonic waves detected.The vibrator is a piezoelectric element or may be an element stablyoscillating vibration frequency, such as an electromagnetic actuator, apiezo element, a crystal vibrator, a ceramic oscillator or amagnetostrictor.

As the effect synergistically obtained, water droplets and stainsattached to the protective glass can be removed by mounting theultrasonic generating element 50 as a sensor and irradiating theprotective glass with ultrasonic waves.

By the above, a sensor module equipped with a protective member, havingboth properties of various sensor functions such as detection of adistance and removal of stains and the chemically strengthened glasshaving high rigidity is provided.

EXAMPLES

The present invention is described below based on specific examples, butthe invention is not construed as being limited to the followingexamples.

Examples 1 to 5 and Comparative Examples 1 to 4

Large-sized plate glasses A to E having a thickness of 0.5 mm consistingof aluminosilicate glass manufactured by a float process were prepared.Those aluminosilicate glasses had the following compositions in masspercentage on oxide basis.

Glass A: SiO₂: 60.9%, Al₂O₃: 12.8%, Na₂O: 12.2%, K₂O: 5.9%, MgO: 6.7%,CaO: 0.1%, SrO: 0.2%, BaO: 0.2% and ZrO₂: 0.1%

Glass B: SiO₂: 60.9%, Al₂O₃: 16.8%, Na₂O: 15.6%, MgO: 5.3%, K₂O: 1.2%,ZrO₂: 0.3% and TiO₂: 0.1%

Glass C: SiO₂: 71.6%, Al₂O₃: 1.9%, Na₂O: 13.4%, K₂O: 0.3%, MgO: 4.7%,CaO: 7.8% and ZrO₂: 0.2%

Glass D: SiO₂: 59.9%, B₂O₃: 7.7%, Al₂O₃: 17.2%, MgO: 3.3%, CaO: 4.1%,SrO: 7.7% and BaO: 0.1%

Glass E: SiO₂: 69.6%, Al₂O₃: 12.6%, Li₂O: 3.9%, Na₂O: 5.4%, K₂O: 1.6%,MgO: 4.7%, CaO: 0.2% and ZrO₂: 2.0%

Subsequently, protective members of Examples 1 to 5 and ComparativeExamples 1 to 3 were produced from the glasses A to E through (1) plateglass cutting step, (2) machining step, (3) polishing step, (4-1)chemical strengthening step or (4-2) physical strengthening step and (5)laminating step shown below. Glass material used in each example isshown in Table 1. Glass plates having desired thickness weremanufactured by adjusting tensile speed of a glass when producing aglass and conducting polishing and etching as necessary.

The protective member of Comparative Example 4 was produced using aresin in place of a glass.

(1) Plate Glass Cutting Step

The plate glass was cut into a given size using a diamond blade.

(2) Machining Step

Subsequently, the end surface of the glass cut was subjected tomachining.

(3) Polishing Step

The glass subjected machining was mirror-polished. By this, a glasshaving surface roughness Ra of a main surface of 100 nm or less wasformed.

(4-1) Chemical Strengthening Step

Examples 1 to 3

A molten salt of potassium nitrate (KNO₃) was heated to 430° C., and theglass subjected to the polishing step was immersed in the molten saltfor 5 hours in Examples 1 and 3 and for 7 hours in Example 2 to performa chemical strengthening treatment. After the chemical strengtheningtreatment, the glass was washed with ion-exchanged water at from 50 to90° C. two times, washed with a running ion-exchanged water of roomtemperature and then dried at 60° C. for 2 hours.

Example 4

In Example 4, the chemical strengthening treatment was conducted in twostages. Specifically, the glass E subjected to the polishing step wasimmersed in a molten salt consisting of 100% NaNO₃ heated to 450° C.,for 2.5 hours. After cleaning, the glass was immersed in a molten saltconsisting of 100% KNO₃ heated to 425° C., for 1.5 hours, followed bycleaning. Thus, a chemically strengthened glass was obtained. Thosecleanings were conducted in the same manner as in Examples 1 to 3.

(4-2) Physical Strengthening Step

Example 5

The glass C subjected to the polishing step was maintained in anelectric furnace at a rapid cooling initiation temperature (the vicinityof a softening temperature) for 5 minutes, taken out of the electricfurnace and allowed to cool in the atmosphere, thereby performingphysical strengthening.

(5) Laminating Step

After the chemical strengthening treatment or physical strengtheningtreatment, the plate glass obtained was laminated to a cylindricalsupport part made of a glass with an adhesive layer. Thus, protectivemembers of Examples 1 to 5 and Comparative Examples 1 to 4 wereprepared.

Evaluation Step

Evaluation of the protective member (glass or resin) of each example wasconducted by the following analytical method.

In the evaluation of transmittance of the protective member,transmission spectrum in a wavelength region of from 300 to 1000 nm wasmeasured using a spectrophotometer (U-4100 manufactured by HitachiHigh-Technologies Corporation). The minimum value Tmin in a wavelengthregion of from 400 to 800 nm was calculated.

Surface compressive stress value (CS) and depth of compressive stresslayer (DOL) of the strengthened glass were measured using a glasssurface stress meter FSM-6000 or SLP-1000 manufactured by OriharaIndustrial Co., Ltd.

TABLE 1 Chemical strengthening conditions (First stage) (Second stage)Surface Depth of Chemical Chemical compressive compressive strengtheningstrengthening Glass Thickness stress CS stress layer DOL ExampleStrengthening Molten salt Temp/time Molten salt Temp/time material (mm)(MPa) (μm) Ex. 1 Chemical KNO₃ 430° C. — — Glass A 1.0 700 45strengthening 100 wt% 5 hours Ex. 2 KNO₃ 430° C. — — Glass B 1.0 1100 45100 wt% 7 hours Ex. 3 KNO₃ 430° C. — — Glass C 1.0 600 10 100 wt% 5hours Ex. 4 NaNO₃ 450° C. KNO₃ 425° C. Glass E 1.0 800 150 100 wt% 2.5hours 100 wt% 1.5 hours Ex. 5 Physical — — — — Glass C 3.0 110 500strengthening Comparative Non- — — — — Glass A 1.0 — — Ex. 1strengthening Comparative — — — — Glass B 1.0 — — Ex. 2 Comparative — —— — Glass D 1.0 — — Ex. 3 Comparative — — — — Resin 2.0 — — Ex. 4Rigidity evaluation (stepping stone Light Light Removal of Crack Heatresistance Comprehensive Example test result) transmittance resistancewater droplets resistance evaluation evaluation Ex. 1 ∘ ∘ ∘ ∘ ∘ ∘ ∘ Ex.2 ∘ ∘ ∘ ∘ ∘ ∘ ∘ Ex. 3 Δ ∘ ∘ ∘ ∘ ∘ ∘ Ex. 4 ∘ ∘ ∘ ∘ ∘ ∘ ∘ Ex. 5 Δ ∘ ∘ ∘ ∘∘ ∘ Comparative x ∘ ∘ ∘ x ∘ x Ex. 1 Comparative x ∘ ∘ ∘ x ∘ x Ex. 2Comparative x ∘ ∘ ∘ x ∘ x Ex. 3 Comparative x ∘ x ∘ x x x Ex. 4

Evaluation results evaluating rigidity, light transmitting property,weather resistance, removal of water droplets by ultrasonic irradiation,cracking of glass by ultrasonic irradiation and heat resistance to theprotective member of each example are shown in Table 1. For example,rigidity evaluation of “∘” shows that the protective member hassufficient rigidity necessary in the case of arranging outdoors a sensormodule equipped with the protective member and “Δ” shows that theprotective member does not satisfy necessary rigidity in a part of theresults. “x” shows that necessary rigidity is not satisfied in allcases.

1. Rigidity Evaluation (Stepping Stone Test Result)

Rigidity evaluation (stepping stone test) was carried out to theprotective member of each example. Deformation amount of a protectivematerial when a certain force is applied is required to be small inorder to protect a sensor and in order that the internal sensormaintains certain sensing function. The rigidity evaluation wasconducted based on the conditions of JASO M104. Specifically, granite(gravel) having a size of from 9 to 15 mm as an emanation was ejected atan angle of 90° in an ejection distance of 350 mm three times. The testwas conducted changing an ejection pressure, and the rigidity wasevaluated as follows. The case where the protective member was broken bythe ejection pressure of 0.1 MPa was evaluated as “x”, the case wherethe protective member was not broken by the ejection pressure of 0.1 MPabut was broken by the ejection pressure of 0.2 MPa was evaluated as “Δ”,the case where the he protective member was not broken by the ejectionpressure of 0.2 MPa but was broken by the ejection pressure of 0.4 MPawas evaluated as “∘”, and the case where the protective member was notbroken by the ejection pressure of 0.4 MPa was evaluated as “∘∘”. Theresults are shown in Table 1.

2. Crack Evaluation

The protective material is required to be not broken when deformation isapplied to the protective material. Ring-on-ring test was conducted tothe protective member of each example using a jig having upper ring: 10mm and lower ring: 30 mm by an autograph manufactured by ShimadzuCorporation. The protective member of each example was processed into asample having a size of 50 mm×50 mm×1 mm. The case where the sample wasbroken when 600 MPa or more of tensile stress was applied was indicatedas “∘”, and the case where the sample was broken when less than 600 MPaof tensile stress was applied was indicated as “x”. The resin(Comparative Example 4) was not broken, but deformation amount was largeand there was a concern of bringing into contact with an internal sensorwhen force was applied. For this reason, the resin was evaluated as “x”.As a result, it was understood that the glasses subjected to thestrengthening treatment of Examples 1 to 5 had rigidity and crackresistance necessary for protecting the sensor. On the other hand, itwas understood that the glasses not subjected to the strengtheningtreatment (Comparative Examples 1 to 3) and the resin (ComparativeExample 4) did not have sufficient rigidity and crack resistance.

3. Light Transmittance

Transmission spectrum in a wavelength region of from 400 to 800 nm ofthe protective member of each example was measured. In a sample having asize of 50 mm×50 mm×1 mm obtained by processing the protective member ofeach example, the sample having Tmin of 85% or more was evaluated as “∘”and a sample having Tmin of less than 85% was evaluated as “x” As aresult, it could be confirmed that regardless of the presence or absenceof the strengthening treatment, each glass and the resin cover showedgood results.

4. Weather Resistance

Resistance (weather resistance) to weathering and heat shock when asensor module equipped with the protective member of each example wasarranged outdoors was evaluated by the following tests.

The evaluation of weather resistance was conducted by both a testholding the protective member of each example at a temperature of 60° C.and a humidity of 80% for 100 hours and thereafter a test irradiating UVlight having a wavelength of 300 nm or less for 10 hours. Afterconducting those tests, the protective member in which its surface wasslightly cloudy white (weathering) in appearance was evaluated as “Δ”,the protective member showing no change was evaluated as “∘” and theprotective member that was deformed and discolored was evaluated as “x”As a result, it could be confirmed that each glass excluding the resincover (Comparative Example 4) showed good results.

5. Removal of Water Droplets

Ultrasonic vibrator was arranged in the protective member of eachexample and irradiated with ultrasonic waves, and whether water dropletsattached to the protective member can be removed (evaluation: ∘) orcannot be removed (evaluation: x) was evaluated. As a result, the effectof removing water droplets could be confirmed in all of the protectivemembers, but cracking occurred in non-strengthened glasses (ComparativeExamples 1 to 3). On the other hand, cracking did not occur in thestrengthened glasses (Examples 1 to 5).

6. Heat Resistance Evaluation

Transparent heater was embedded in the protective member of eachexample, and after allowing to stand the protective heater at anelevated temperature for a certain time, its appearance was evaluated.Specifically, the protective member was held at 100° C. for 1 hour, andthe presence or absence of remarkable deformation and discoloration wasthen visually observed. The protective member having deformation anddiscoloration is indicated as “x” and the protective member free ofdeformation and discoloration is indicated as “∘”. As a result, it wasunderstood that the protective members using a glass of Examples 1 to 5and Comparative Examples 1 to 3 showed good results.

Comprehensively judging from the evaluation results of the above 1 to 6,it was understood that the performance of the protective member stronglydepended on a compressive stress value (CS) and a depth of a compressivestress layer (DOL) after the strengthening treatment due to thecomposition of a glass. Furthermore, it was understood based on theevaluation results obtained that CS and DOL of the protective glass werepreferably DOL being 10 μm or more and CS being 100 MPa or more, andmore preferably DOL being 40 μm or more and CS being 600 MPa or more.

Examples 6 to 10

Protective members of Examples 6 to 10 were produced using glass Ethrough (1) plate glass cutting step, (2) machining step, (3) polishingstep, (4-1) chemical strengthening step and (5) laminating step, andwere evaluated by 1 to 6 above.

The chemical strengthening treatment in Examples 6, 7 and 10 wasconducted in two stages. Specifically, the glass E after the polishingstep was immersed in a molten salt consisting of 100% NaNO₃, washed,immersed in a molten salt consisting of 100% KNO₃, and washed. Thus, achemically strengthened glass was obtained. The treatment temperatureand time are show in Table 2.

The chemical strengthening treatment in Examples 8 and 9 was conductedin one stage. Specifically, the glass E after the polishing step wasimmersed in a molten salt consisting of 100% NaNO₃ and washed. Thus, achemically strengthened glass was obtained. The treatment temperatureand time are show in Table 2.

Examples 11 to 13

Protective members of Examples 11 to 13 were produced using the glass Bthrough (1) plate glass cutting step, (2) machining step, (3) polishingstep, (4-1) chemical strengthening step and (5) laminating step, andwere evaluated by 1 to 6 above.

The chemical strengthening treatment was conducted in one stage.Specifically, the glass B after the polishing step was immersed in amolten salt consisting of KNO₃ and a specific weight ratio of Na₂NO₃added thereto, and then washed. Thus, a chemically strengthened glasswas obtained. The weight ratio between KNO₃ and Na₂NO₃ in the moltensalt and the treatment temperature and time are shown in Table 2.

TABLE 2 Depth of Chemical strengthening conditions Compressive stress CScompressive (First stage) (Second stage) Surface Deep layer Deep Layerstress layer Chemical strengthening Chemical strengthening GlassThickness CS 100 μm CS 200 μm CS DOL Example Molten salt Temp/timeMolten salt Temp/time material (mm) (MPa) (MPa) (MPa) (μm) Ex. 6 NaNO₃:100 wt% 450° C. KNO₃: 100 wt% 425° C. Glass E 2.0 941 80 7 217 2.5 hours1.5 hours Ex. 7 NaNO₃: 100 wt% 450° C. KNO₃: 100 wt% 425° C. 2.0 954 10843 304 15 hours 1.5 hours Ex. 8 NaNO₃: 100 wt% 450° C. — — 2.0 264 11949 351 24 hours Ex. 9 NaNO₃: 100 wt% 450° C. — — 3.2 242 145 85 541 48hours Ex. 10 NaNO₃: 100 wt% 450° C. KNO₃: 100 wt% 425° C. 3.2 930 115 70550 48 hours 1.5 hours Ex. 11 KNO₃: 95 wt% 430° C. — — Glass B 2.0 71892 — 140 NaNO₃: 5 wt% 96 hours Ex. 12 KNO₃: 95 wt% 430° C. — — 2.0 762 —— 85 NaNO₃: 5 wt% 24 hours Ex. 13 KNO₃: 96 wt% 475° C. — — 2.0 760 — —41 NaNO₃: 4 wt% 3 hours Rigidity evaluation (stepping stone LightWeather Removal of Crack Heat resistance Comprehensive Example testresult) transmittance resistance water droplets resistance evaluationevaluation Ex. 6 ∘ ∘ ∘ ∘ ∘ ∘ ∘ Ex. 7 ∘∘ ∘ ∘ ∘ ∘ ∘ ∘ Ex. 8 ∘ ∘ ∘ ∘ ∘ ∘ ∘Ex. 9 ∘∘ ∘ ∘ ∘ ∘ ∘ ∘ Ex. 10 ∘∘ ∘ ∘ ∘ ∘ ∘ ∘ Ex. 11 Δ ∘ ∘ ∘ ∘ ∘ ∘ Ex. 12 Δ∘ ∘ ∘ ∘ ∘ ∘ Ex. 13 Δ ∘ ∘ ∘ ∘ ∘ ∘

From the results of Table 2, in the protective members (chemicallystrengthened glasses) obtained in Examples 6 to 13, cracking did notoccur under at least an ejection pressure of 0.1 MPa based on JASO M104in the rigidity evaluation (stepping stone test result). Furthermore,the desired evaluation result was obtained in each of lighttransmittance, light resistance, cracking evaluation and heat resistanceevaluation.

Examples 14 to 16

Flat plate-shaped glass E having a thickness of 6 mm was subjected tomachining to form a dome-shaped glass having an inner radius of 18 mm(inner diameter: 36 mm), an outer radius of 20 mm (outer diameter: 40mm) and a thickness (wall thickness) of 2 mm. The surface of the glassplate after machining was polished. Surface roughness Ra of the convexsurface and concave surface was 8 nm, and surface roughness Ra of theend surface was 0.15 μm. In this case, the dome-shaped glass plate was apartially hemispherical glass having a horizontal width of 25 mm and aheight of 5.3 mm. Thereafter, the partially hemispherical glass wasimmersed in a molten salt consisting of 100% NaNO₃, washed, immersed ina molten salt consisting of 100% KNO₃ and then washed. Thus, theprotective members (partially hemispherical chemically strengthenedglasses) of Examples 14 and 15 were obtained. Protective member(partially hemispherical chemically strengthened glass) of Example 16was obtained using the flat plate-shaped glass E having a thickness of 6mm in the same manners as above, except for forming a dome-shaped glasshaving an inner radius of 16.8 mm (inner diameter: 33.6 mm), an outerradius of 20 mm (outer diameter: 40 mm) and a thickness (wall thickness)of 3.2 mm. The chemical strengthening treatment temperature and time areshown in Table 3. Rigidity of the protective members obtained ofExamples 14 to 16 was evaluated.

TABLE 3 Chemical strengthening conditions (First stage) (Second stage)Chemical strengthening Chemical strengthening Thickness Example Moltensalt Temp/time Molten salt Temp/time Glass material (mm) Ex. 14 NaNO₃:100 wt% 450° C. KNO₃: 100 wt% 425° C. Glass E 2.0 2.5 hours 1.5 hoursEx. 15 NaNO₃: 100 wt% 450° C. KNO₃: 100 wt% 425° C. 2.0 15 hours 1.5hours Ex, 16 NaNO₃: 100 wt% 450° C. KNO₃: 100 wt% 425° C. 3.2 48 hours1.5 hours Compressive stress CS Convex surface Concave surface SurfaceCS of DOL of convex Depth of Depth of convex surface - surface - Surfacecompressive stress Surface compressive stress surface CS of DOL ofconcave Rigidity evaluation CS layer DOL CS layer DOL concave surfacesurface (stepping stone test Example (MPa) (μm) (MPa) (μm) (MPa) (μm)result) Ex. 14 946 227 936 207 10 20 ∘ Ex. 15 964 324 944 284 20 40 ∘∘Ex. 16 945 590 920 510 25 80 ∘∘

From the results of Table 3, the partially hemispherical chemicallystrengthened glasses (protective members) obtained in Examples 14 to 16were that cracking did not occur under at least an ejection pressure of0.2 MPa based on JASO M104 in the rigidity evaluation (stepping stonetest result), thus showing high rigidity.

According to this embodiment, a sensor module having excellent rigidity,scratch resistance and weather resistance and suitable for outdoor usescan be provided.

Although the preferred embodiment of the present invention is describedin detail below, but the present invention is not construed as beinglimited to the above-described specific embodiments and variousmodifications or changes can be made in the range of the gist of thepresent invention described in the scope of the claims.

Although the present invention has been described in detail and byreference to the specific embodiments, it is apparent to one skilled inthe art that various modifications or changes can be made withoutdeparting the spirit and scope of the present invention. Thisapplication is based on Japanese Patent Application No. 2017-132137filed Jul. 5, 2017, the disclosure of which is incorporated herein byreference in its entity.

REFERENCE SIGNS LIST

-   -   1: Protective member    -   2: Support part    -   5: Mounting part    -   10: Protective glass    -   15: Base member    -   20: Sensor    -   25: Power source    -   30: Camera    -   40: Vibrator    -   50: Ultrasonic generating element    -   60: Transparent heater

1. A sensor module comprising: a base member; at least one of a singleor a plurality of sensors and vibrators arranged on the base member; anda protective member constituted of at least one flat surface or a curvedsurface, provided so as to cover the at least one of the sensors and thevibrators, wherein a part or whole of the protective member is formed ofa strengthened glass and the strengthened glass is a chemicallystrengthened glass or a physically strengthened glass.
 2. The sensormodule according to claim 1, wherein the strengthened glass has asurface compressive stress value of 400 MPa or more and a depth ofcompressive stress layer of 10 μm or more.
 3. The sensor moduleaccording to claim 2, wherein the strengthened glass has the surfacecompressive stress value of 600 MPa or more and the depth of compressivestress layer of 40 μm or more.
 4. The sensor module according to claim1, wherein the strengthened glass is a chemically strengthened glass andhas a thickness of from 0.5 mm to 3.5 mm.
 5. The sensor module accordingto claim 1, wherein the strengthened glass is a chemically strengthenedglass, has a thickness of from 1.5 mm to 3.5 mm, and has a depth ofcompressive stress layer in a range of from 200 μm to 580 μm.
 6. Thesensor module according to claim 5, wherein the chemically strengthenedglass has a surface compressive stress value of 700 MPa or more.
 7. Thesensor module according to claim 5, wherein the chemically strengthenedglass has the depth of the compressive stress layer in a range of from250 μm to 580 μm, and has a compressive stress value at a depth of 100μm from a surface of 100 MPa or more.
 8. The sensor module according toclaim 5, wherein the chemically strengthened glass has a curved surfaceshape having a convex surface and a concave surface, and a valueobtained by subtracting a surface compressive stress value of theconcave surface from a surface compressive stress value of the convexsurface is 10 MPa or more.
 9. The sensor module according to claim 8,wherein a value obtained by subtracting a depth of compressive stresslayer of the concave surface from a depth of compressive stress layer ofthe convex surface is 10 μm or more.
 10. The sensor module according toclaim 1, wherein the chemically strengthened glass has at least onebending point in a region forming the compressive stress layer and has astress distribution curve having a different inclination with thebending point as a boundary.
 11. The sensor module according to claim 1,wherein the vibrator has an ultrasonic generating element.
 12. Thesensor module according to claim 1, wherein the protective member has atransparent heater.
 13. The sensor module according to claim 1, whereinthe strengthened glass has a first main surface and a second mainsurface facing the first main surface, and has an end surface betweenthe first main surface and the second main surface, and the end surfacehas a surface roughness in a range of from 0.01 μm to 1.0 μm.
 14. Thesensor module according to claim 1, wherein the strengthened glass is aglass ceramics.
 15. The sensor module according to claim 1, wherein thestrengthened glass has a water-repellent film on the surface of thestrengthened glass.
 16. A protective glass constituted of a flat surfaceor a curved surface, wherein a part or whole of the protective glass isa strengthened glass, and the strengthened glass is a chemicallystrengthened glass or a physically strengthened glass.
 17. Theprotective glass according to claim 16, having an ultrasonic vibrator.18. The protective glass according to claim 16, having a transparentheater.